Infectious diseases, such as that caused by Herpes Simplex Virus (HSV), are conventionally assayed by extracting body fluids, such as pus, from sores, and then extracting appropriate antigens from these fluids. Once the antigens are extracted, if present, they are passed through a filter to remove extraneous material, and then assayed in an immunoassay such as the device taught in commonly assigned U.S. Ser. No. 240,179 filed on Sept. 6, 1988, by Hinckley et al, which is a continuation-in-part application of U.S. Ser. No. 098,248 filed on Sept. 18, 1987, entitled "Sliding Valve for Vent of Liquid Collecting Compartment", now abandoned. Such a device has a membrane that captures the complexed antigen and antibodies used in the test, but allows unbound substances to pass through. This is sometimes called the bound/free separation step.
In certain tests, such as the HSV test, standard filtering has not been adequate to remove all the extraneous particulate matter. As a result, the extraneous particles end up on the membrane of the immunoassay device, clogging it and delaying the necessary flow-through of the free liquid and unbound substances such as labels.
Therefore, prior to this invention there has been a need to obtain antigens extracted from body fluids so as to render them more processable in a test device that uses a filter to separate bound substances from free substances.